Oil burner



April 30, 1957 E K, SMITH 2,790,490

OIL BURNER Filed Nov. 1, 1954 4 F/G. sT

EARL K. SMITH ATTORNEYS INVEN-TOR n di lt siswlfatsfi v This inventionrelates generally to liquid fuel burners and'more particularly to an oilburner of the gun type having novel air-directing, proportioning, andbaffling means. V V r 4 n It is a primary object of this invention toprovide a liquid fuel burner having novel means for maintaining anautomatically self-compensating volumetric equilibrium of the overallcombustion air supply. I

It is another object of this invention to provide a burner constructionhaving novel air-directing proportioning, and battling means operativeto first form partial vacuum zones, one immediately upstream and theother immediately downstream of the fuel spray nozzle tip, and to thencooperate with the fuel spray cone: to automatically maintain therelative locationj alndyol' umesof the partial vacuum zones over apredetermined range of fuel flow rates; 7 b n It is a further object ofthis invention to provide a gun-type oil burner having fixedlypositioned arid nlonadjustable air-directing; proportioning, andbafliing meaiis' for automatically" maintaining balanced streams ofi airflow, wherein said air-directing, proportioning', and bathingmeanscooperates with'thefuel spray cone in a s6 as to permit the latter toautomatically apportion and control both primary and secondary air newv'oltiiiieso v a range of fuel flow rates of from 0.65 to 1.65 gallonsper hour. r

It is still another object to provide air-directih a p o portioning, andbattling-means cooperatin with e sp y cone of a'liquid fuel burner toetfectself c'ompensahng ratio control of the primary and secondary airnew volumes under lovi oi" re stuaaaermardraft co tibnsi It is still afurther object to provide a guii-typjoilf burner having a fixed aridnon-adjustable thio'a't iirig assembly surrounding the spray nozzle tipadjacnt'the' mouth of the blast tube, and further having a' hired butremovable disc baffle mounted upstream'of th'nozzle tip, saidthroat-ring assembly and disc baffle havmg'fixaareas and cooperatingwith the oil spray cone" to enable it to automatically control thevolumetric ratio ofp r imary and secondary air supply without any needfor niecha'r'i ical adjustment of parts. V n I It is ye't another objectto provide a burner construction permitting substantially pulsation-freeor nozzle? combustion, whereinthe flame is established at a maximumdistance from' the fuel nozzle tip, without the necessity for auxiliaryventing the combustion chamber. With these and other objects in view,'myinvent 1i consists in the construction, arrangementan'd cornbi tion ofthe various parts of my oil burner whereby the objects contemplated areobtained as h'ereina fter' are? fully set forth, pointed out in myclaims and illustrated in the accompanying drawing, whereini V r IFigure 1 is a top plan view, partly broken aw ay aiid in horizontalcross-section, of the blast tube and'noiz zle assembly of a gun-type oilburner constructed in accordance with the'present' invention;

2,799,490 r. th n? p 6. 1957 sigma 2" is an endelevational view, lookingin the direction indicated at 2-2 on Figure 1; v

Figure 3 is a vertical cross-section taken substantially as'indica tedby the line 3-3 on Figure 1;

Figure 4 is' another vertical cross section taken substantially asindicated by the line 4 4 of Figure 1; and

Figure 5 is a diagrammatic view illustrating the paths of movement ofthe air flow through the burner during Pq a fi-.

Referring now to the drawing I have indicated at 1 0 the air or blasttube of a gun-type oil burner constructed in" accordance with thepresentinvention. The rearend of the blast tube 10 is provided with a mountingflange 12 for attaching the tribe to an air blower in the wellknownrrianne'rl The" forward end of thetu'be 10 carries a terminal end ring14 The end ring 14 provides a cylindrical side wall portion and aconverging frusto oriicalterifiinal' portion, and is preferably formedas a single unitar casting.

vTheblast tub'e'terrninal end' ring 14 provides a circular diseha'rgmouth 16 A plurality of helical vanes 18 x 'tend'ihwardly from the ring14, and may be integrally cast as" portions of the ring, or may beseparate vane members suitably attached thereto, as; by welding." M KAth'rdat forming rin'g 20'is centrally disposed in can; centric"rel'ation' Within the end ring 14" and" th'e" helical vanes 18, and isrigidly secured to the inner longitudinal edges" of the" helical vanes18, as" by welding.- An annular colla'r flange 22 is" s' cured'tobthr'iiig'Zl)" at its inner end; aiid'pro'vid'es a radially outwardlyextending surface The" collar ange" 22 also prdvides a radially inwardlextending ba'fiie portion 24," which may be f'drnid as a separateannular ring or as an integ'ral ex} tension of the throat ring 20 orcollar flange 22 The forward end of the throat ring 20 provides acircular m0ut1i'26,which is slightly upstream and inwardly spaed a fineddistance from the mouth formeaby'rhei terminal end ring 14. The" throatring 20aiid the cooperating annular flange acetone 22 and 24 constituteaunitary threat assembl This fixed ositioning of parts re resentsa'highly important feature of this invention. b The-' outer peripheraledge of the annular collar flange 22 terminates indefinite spacedrelation toth cylindrical pdr'tio'nof the blast tube IOandterm'inal, andring 14, in concentric relation therewith. The relative spacing of theseparts provides an annular inlet passageway 25 for air how into the spaceor chamberdefined between th'e outer periphery of the collar fla'nge 22and the rear inner wall portion of thetrfminal end ring 14. The forwardends of the end ring l4" and the throat ring 20 are spaced so as toprovide an an nulanoutletpas'sageway 27 for airflow therebetween. The'relative spacing of the various parts is predetermined so that the flowarea, of the annular in'let and outlet passageways 2 5 and 27 of thechamber defined betweenrings 14 and '20 are substantially equal. It willbe apparent that this space; or chamber'between rings 1 4 and, in whichthe helical vanes 18 are disposed, provides'a flow-enlargement spacebetween the annular inlet and outlet passageways 25 and'27. In thismanne 'r; p'lnrality of small cushioning bodies of volumes of' ai'r are'provided for steadyiug the flow therethrough across the helical vanes18. These cushioning vdlu-mes serve to equalize small fluctuations. inthe rate of air flow so as to permit a steady and even'fiow of air pastthevanes 1s. v V

An oil pipe 28 is centrally positioned within the blast tube 10 andextends longitudinally therein; The for- Ward end of the oil pipe 28carries a spray nozzle 30. The orifice end of the spray nozzle 30terminates within the throatiring 29', preferably at adistanc in therange, of about V2 to of an inch upstream of the discharge 3 mouth 16. Ifind the most desirable spacing to be at a distance of about bi of aninch.

A disc or baflle plate 32 is fixedly secured to the oil pipe 23. Theplate 32 provides a supporting means for centrally positioning the oilpipe 28 within the blast tube 10. The plate 32 is of smaller diameterthan the blast tube 10, and is provided with a plurality of radiallyoutwardly extending legs 34 which engage the walls of the blast tube forcentering and supporting the plate 32 therein. The spaced relationshipof the outer periphery of the plate 32 and the side wall of the blasttube 10 serves to provide an annular flow passageway 36 about the plate32 closely adjacent the walls of the blast tube 10.

I have particularly designed the burner construction of the presentinvention for use within an operating range of fuelflow rates of from0.65 to 1.65 gallons per hour (G. P. H.), inclusive. It is important atthese flow rates to select the flow-obstructing area of the baflie plate32 so as to be equal to 65% of the total cross-sectional area of the airblast tube 10. Further, it is also highly important to position thebaifle 32 within the blast tube '10 at a point upstream from thedischarge mouth 16 a distance equal to the diameter of the blast tube10. In addition, the annular inlet and outlet passages 25 and 27adjacent the end edges of the vanes 18 and between the terminal end ring14 and the throat ring 20 are predetermined so as to each have a totalflow area equal to about one-half of the annular passageway 36. Thisoptimum selection of areas and positioning of parts permits a constant,non-adjustable relation of allmetallic components of the air directing,proportioning. and bafliing parts of the burner. Once the initialselection of baflie areas and positions has been made, variations in thechoice of fuel nozzle orifice size alone, in the specified fuel flowrange, will effect control of the ratio of primary and secondary airvolume to support combustion during burner operation without thenecessity for any adjustment of parts.

The baffle plate 32 is formed with a central boss which is suitablyapertured to receive the oil pipe 28 therethrough. 'Insulated supports40 of a pair of electrode wires 42 extend through complementary cutawayportions of the plate 32 and a removable segment portion 44 thereof. Aset screw 46 servest-o secure the insulated supports 40 in fixedposition, as clearly shown in Figure 4 of the drawing.

Operation By means of the novel arrangement of the metal parts of myburner construction, and particularly the co-relation between the discbaflie and the throat ring assembly, -as described above, I haveprovided a wholly new and improved operation for a liquid fuel 'burner.I have provided constant-area and non-adjustable relations of aircontrol components capable of achieving smooth, eflicient, and quietoperation at all fuel flow rates within the relatively low flow range of0.65 to 1.65 G. P. H., inclusive. The optimum operating conditions formy burner are approached as draft conditions are lowered to a mini-mumvalue very nearly equal to atmospheric pressure. My novel constructionwholly eliminates any need for auxiliary venting to eliminate flamepulsations, and makes it possible to position the base of the flame at amaximum distance of about 3 to 4 inches from the mouth of the burnerblast tube,

manner. The quantity of this total inlet air is predeter-' mined by theusual means of adjusting the free area at the blower fan inlet atconstant fan speed so as to provide the necessary total air volume forsupporting combustion at the particular rate of fuel flow which ispredetermined by the particular nozzle tip size and spray angle whichhave been selected. The air is then automatically apportioned within theblast tube by means of my disc baflie and throat ring assembly, incooperation with the oil while at the same time maintaining combustionstability,

spray cone, into the proper volumetric ratio of primary and secondaryair streams.

The primary air stream is the peripheral air flow adjacent the blasttube walls, and constitutes the major volume of combustion air. Thesecondary air stream is the air flow at the center of the blast tubeadjacent the oil nozzle tip. The primary air is of greater volume thanthe secondary air because of the positive baffling effect of thebarriers 32 and 22, and the barrier effect of the oil spray cone(indicated in dot-dash lines on Figures 1 and 5). The separation of theoverall volume of inlet air into primary and secondary streams of flowserves to establish and balance the two partial vacuum zones (indicatedin Figure 5 at 50 and 52) in a manner so as to maintain flameeuqilibrium, over a range of flame sizes at various fuel flow rates,without the need for any mechanical adjustment of parts.

As clearly shown in Figure l of the drawing, the throat ring 20 providesno positive means for imparting any whirling motion to the secondaryair, but merely constitutes an unobstructed tunnel or flow throat. Allwhirling motion of the secondary air after leaving the throat mouth 26is imparted by the whirling motion of the oil spray and natural draftconditions alone, and the air is not forced into such motion by means ofstatic pressures ordinarily employed or any structural means. Thepositive whirling means conventionally employed by the prior art toefiect a swirling of the combustion supporting air under static pressurefor mixture with the oil spray cone, at conventional oil pressures ofabout p. s. i., cannot be eificiently synchronized with the flow ofcombustion supporting air, at conventional air pressures of about $6inch of water column, or with the different spray cone sizes of variousfuel flow rates employed. In my construction, the whirling oil sprayitself induces or aspirates all of the combustion supporting air it mayrequire, thereby merging into the flame the outer (primary) and inner(secondary) air through the paths provided, at a synchronized rate bothas to volume and direction, and in accordance with the physical filmstrength or skintension of the hollow oil spray cone. In this manner,the oil cone itself does its own regulating or apportioning of therequired primary and secondary air volumes. The oil cone itself alsoserves both as a baffle, to hold back excess secondary air, and as aninduced feeding means to aspirate the larger volume of primary airrequired for efficient combustion. It should be noted that the primaryair is introduced at the outer periphery of the discharge mouth16,-where the skin-tension of the oil spray begins to disintegrate, thusdelivering it in an uninterrupted flow to the core of the flame.

The term draft is defined as the negative pressure condition whichprevails between the zone above the visible flame of combustion and thetop of the flue or stack through which the products of combustion aredisposed of or vented. The draft pressure is distinguished from theblower pressure which prevails in the blast tube.

'rr'rr'abiy, my burner construction is operated at a stack pressurewhich is slightly less than atmosphefi'c pressure. Such a pressure istermed a negative? pressure in that it results in a gauge reading whichis lessth an atmospheric. Reference to negative pressures in the presentdescription is intended to mean pressure below atmospheric, andtherefore constituting a slight vacuum condition.

It is' of particular importance that my construction, is capable; ofsmooth, noiseless, and eificient operation under less than normal draftconditions. I have also achieved highly satisfactory performance underconditions wherein the draftpressure is zero or slightly positive (inexcess of atmospheric pressure). By utilizing the physical force effectsof the oil spray ihestablishing the flame, I am able to achieve uniformperformance despite wide variations in the draft conditions. It will beapparent that upon initiationof combustion, the consequent heated airsurrounding the flame will rise by natural convection and cause apressure differential to be established, thereby creating a draftsubstantially immediately after ignition.

The hollow oil spray cone provides a barrier or separating wall betweenthe partial vacuum zone 50 at the forward end of the blast tube and thepartial vacuum zone 52 which prevails at the core of the oil spraywithin the combustion chamber. The spray cone has its apex at the nozzleorifice, and is preferably delivered at the conventional oil flowpressure of about 100 p. s. i The oil cone itself acts to aspirate orcarry forward the flow of air from the burner blast tube intothe'combustion zone. The actual physical strength or skin-tensionlof thecoil cone immediately adjacent the nozzle orifice is proportional to therate of oil new, Thisls'trength is greater at the apex of the oil coneand diminishes as the cone enlarges outwardly. Since the volume of airwhich will he aspirated by the spray cone is dependent upon the physicalstrength of the forward flowing oil, it will be apparent that the supplyof air from the burner blast tube which is induced into the combustionzone. will be greatest where the skin-tension begins to disintegrate(where the outer or primary air is introduced'at outlet 27), and will beleast where the skin-tension is greatest (where the inner or secondary.air is introduced as an induced slip-stream at the mouth 2 6). In' thisway, both air streams are controlled and regulated in aselfcompensatingmanner in response to variations in the oil flow over a range of 0.65 to1.65 G. P. H. s v I v The blower fan operates under intake conditionswhich cause the fan to be starved for the overall air supply requiredfor highest combustion efficiency at the'prede termined rate of oilflow. In this way, the fan strives to move all of the air which isavailable to it through the blower intake toward the mouth of theblast'tube, at which point the oil spray cone will operate to positivelyaspirate into the combustion chamber all of the air necessary foroptimum combustion efficiency. It is not possible, however, to whollyeliminate the blower fan, because the oil spray does not have asufficient aspirating power to draw the required air from a remotedistance. Under practical operating conditions, therefore, the pressureswithin the blower fan housingwill be negative. This constitutes animportant forward step over the prior art, wherein the static pressureconditions must necessarily be positive.

Noise is an undesirable operating characteristic of many presently knowndomestic burner constructions. The term noise is generally employed todesignate the loud reverberations or pulsations which are the result ofinterruptions and fluctuations in the combustion process. Such pulsingcombustion is due to spasmodic alternations of the fuel-air mixtureratio between adequate and inadequate oxygen supply. Such pulsingresults in the'base of the flame jumping away from and snapping bactoward a normal position with respect were nozzle orifice; The furtheraway" from the nozzle anaother come combustionpulsations and minimizenoise.

metal parts or the burner that the base of the name is positioned duringoperation, the less will be the'likli hood of undesirable carbonfern-ration which results from contactand radiation by the flame or itsreflected heat upon metal: burner parts which bec m moist with oil. Thefurther away the base of the flame is positioned, however, the morediflicult it becomes to control flame stability, and avoid pulsation andthe risk of havingthe flame flo'at away entirely.

The noise referred to herein is the pulsing or reverberating sound dueto interrupted or irregular burning, and is not the steady sound ofsmoothly merging fuelair mixture which accompanies low-velocity stablecoinbustion. normal steady sound of stable combustion, without the loudpulsation noise of interrupted or irregu lar combustion, is relativelyquiet and may be referred to as substantially noiseless combustion;

The most i'mportant'underlying factor essential to stable combustion isthe manher' in which the" carbon of the fuel and the oxygen of the airare united under conditions of draft in the combustion chamber.Combustion chamher or stackdraft is necessary for relatively completecombustion, and serves the purpose of carrying away the combustionbyproducts. The lower the draft, or the nearer the stack pressureapproaches atmospheric press'u'reythe greater willbe the opportunity foreflicient combustionto'ta'ke place at a relatively slow rate, wherebysubstantially improved heat exchange to the heating plant will he madepossible. Mere slow combustion alone, however, is not sufflcient'unlesssmooth mixing and propoisonin of thecarbon and oxygen elements iseffected. The basic purpose of my burner construction is to lower thedraft pressure and" consequently thevolume of total airflow through'theburner blast tube with a corresponding minimum natural draft'con'dition'within the combustion chamber and stack. In this way, it is possibletosubstantially reduce the excess air requirements, upon which highcombustion efficiency (in conventional installations) necessarilydepends, without producing the adverse effects of smoke, soot, hardcarbon deposits, or odor of unburned gases.

It is common practice inmany of the presently known domestic heatinginstallations to provide a small vent for admitting air directly over orunder the flame to over- AL though by regulating the size of suchventsit is possible under negative draft conditions to equalize the combustion process and correct'the problem of combustion pulsations, thecooling eifect of the excess air thus admitted upon the flamesubstantially reduces combustion efficiency. Further, the practice ofauxiliary venting frequently results in a highly objectionable escapeofcornbustion odors into the room air of a domestic heating installationduring the burner starting cycle. I s

My self-compensating burner construction effectively controls the airsupply to the fuel so as to permit the base of the frame to bepositioned and maintained a maximum distance away from the mouth of theblast tube and all other metal parts. This separating distance is atleast twice that found in conventionalburners, and is maintainedconstant so as to effectively eliminate flame pulsation ann consequentnoise. Further, the need for auxiliary venting is eliminated. V

The essence of my novel structural arrangement is the achievement of afunctional operation, over a design range of low firing rates, whereinthe base of the flame, or the point at which the united flow of oil andair commence to burn with a visible flame, is maintained at a relativelyfixed or stationary position, and at a maximum separating distancedownstream of the nozzle tip and blast tube mouth. My constructionoperates to achieve this function over a range ofstack draft conditionsboth above and below normal draft pressure; Optimum operating conditionsfor my burner construction are ap- 7 proached as draft pressureapproaches an irreducible minimum.

Changes may be made in the construction and arrangement of the parts ofmy oil burner without departing from the real spirit and purpose of myinvention, and it is my intention to cover by my claims any modifiedforms of structure or use of mechanical improvements which may bereasonably included within their scope.

What I claim as new and desire to obtain by Letters Patent of the UnitedStates is:

l. A liquid fuel burner comprising an elongated air blast tube havingits rear end adapted to receive a flow of inlet air and having itsforward end adapted to discharge into a combustion chamber, a batfieplate disposed within said tube, means cooperating with said baffleplate to position it in spaced relation to the walls of said tube anddefine a passageway therebetween, a generally cylindrical ring membercentrally disposed in longitudinally coaxial relation within said tubeforwardly of said baffle plate, said ring defining a central throatpassageway therethrough, an annular collar member secured to the rearend of said ring and providing a bafide surface generally normal to thelongitudinal axis of said ring and entirely rearwardly thereof, saidbaffie surface extending radially inwardly and outwardly of said ringthroat passageway, said ring being spaced from the walls of said tube todefine a chamber therebetween, said radially outwardly extending portionof said collar being spaced from the'walls of said tube to define arestricted inlet passageway into said chamber, the forward end of saidring cooperating with the forward end of said tube to define a dischargepassageway from said chamber, said inlet and discharge passageways beingsubstantially equal in cross sectional area and smaller than the crosssectional area of said chamber, said chamber providing a cushioningvolume for regulating an even discharge of air flow therefrom, and aplurality of vanes in said chamber helically disposed relative to thelongitudinal axis of said tube for imparting a spin to the air flowingtherethrough,

said vanes being positioned radially outwardly of said about 65% of thetotal cross-sectional area of said air blast tube, said baffle platebeing positioned upstream of the discharge mouth of said tube a distancesubstantially equal to the diameter of said blast tube, a generallycylindrical ring member centrally disposed in longitudinally coaxialrelation with said tube forwardly of said baffle plate, said ringdefining a central throat passageway therethrough, an annular collarmember secured to the rear end of said ring and providing a battlesurface generally normal to the longitudinal axis of said ring andentirely rearwardly thereof, said baflle surface extending radiallyinwardly and outwardly of said ring throat passageway, said ring beingspaced from the walls of said tube to define a chamber therebetween,said radially outwardly extending portion of said collar being spacedfrom the walls of said tube to define a restricted inlet passageway intosaid chamber, the forward end of said ring cooperating withthe forwardend of said tube to define a discharge passageway from said chamber,said inlet and discharge passageways being substantially equal in crosssectional area and smaller than the cross sectional area of saidchamber, said chamber providing a cushioning volume for regulating aneven discharge of air flow therefrom, and a plurality of vanes in saidchamber helically disposed relative to the longitudinal axis of saidtube for imparting a spin to the air flowing therethrough, said vanesbeing positioned radially outwardly of said ring and forwardly of saidcollar member. a

3. A liquid fuel burner comprising an elongated air blast tube havingits rear end adapted to receive a flow of inlet air and having itsforward end adapted to discharge into a combustion chamber, a baffleplate disposed within said tube, means cooperating with said baffleplate to position it in spaced relation to the walls of said tube anddefine a passageway therebetween, a generally cylindrical ring membercentrally disposed in longitudinally coaxial relation within said tubeforwardly of said bafile plate, said ring defining a central throatpassageway therethrough, an annular collar member secured to the rearend of said ring and providing a bafiie surface generally normal to thelongitudinal axis of said ring and entirely rearwardly thereof, saidbaiile surface extending radially inwardly and outwardly of said ringthroat passageway, said ring being spaced from the walls of said tube todefine a chamber therebetween, said radially outwardly extending portionof said collar being spaced from the walls of said tube to define arestricted inlet passageway into said chamber, the forward end of saidring cooperating with the forward end of said tube to define arestricted discharge passageway from said chamber, said inlet anddischarge passageways being smaller than the cross sectional area ofsaid chamber, said chamber providing a cushioning volume for regulatingan even discharge of air flow therefrom, and a plurality of vanes insaid chamber helically disposed relative to the longitudinal axis ofsaid tube for imparting a spin to the air flowing therethrough, saidvanes being positioned radially outwardly of said ring and forwardly ofsaid collar member.

4. A liquid fuel burner comprising an elongated air blast tube havingits rear end adapted to receive a flow of inlet air and having itsforward end adapted to discharge into a combustion chamber, a bafileplate disposed within said tube, means cooperating with said baffleplate to position it in spaced relation to the walls of said tube anddefine a passageway therebetween, the flow obstructing area of saidbafile plate being equal to about of the total cross-sectional area ofsaid air blast tube, said baffle plate being positioned upstream of thedischarge mouth of said tube a distance substantially equal to thediameter of said blast tube, a generally cylindrical ring membercentrally disposed in longitudinally coaxial relation with said tubeforwardly of said baffle plate, said ring defining a central throatpassageway therethrough, an annular collar member secured to the rearend of said ring and providing a baffie surface generally normal to thelongitudinal axis of said ring and entirely rearwardly thereof, saidbaffle surface extending radially inwardly and outwardly of said ringthroat passageway, said ring being spaced from the walls of said tube todefine a chamber therebetween, said radially outwardly extending portionof said collar being spaced from the walls of said tube to define arestricted inlet passageway into said chamber, the forward end of saidring cooperating wtih the forward end of said tube to define arestricted discharge passageway from said chamber, said inlet anddischarge passageways being smaller than the cross sectioanl area ofsaid chamber, said chamber providing a cushioning volume for regulatingan even discharge of air flow therefrom, and a plurality of vanes insaid chamber helically disposed relative to the longitudinal axis ofsaid tube for imparting a spin to the air flowing therethrough, saidvanes being positioned radially outwardly of said ring and forwardly ofsaid collar member.

5. A liquid fuel burner comprising an elongated air blast tube havingits rear end adapted to receive a flow of inlet air and having itsforward end adapted to discharge into a combustion chamber, an oil tubeterminating in a spray nozzle upstream of and closely adjacent theforward end of said tube, said nozzle when supplied with oil at apredetermined pressure serving to discharge a spray cone of oil at aflow rate within the range of 0.65 to 1.65 G. P. H., a bafile platedisposed within said tube, means cooperating with said baffle plate toposition it in spaced relation to the walls of said tube and apassageway therebetween, a generally cylindrical ring member centrallydisposed in longitudinally coaxial relation with in said tube forwardlyof said baffle plate, said ring defining a central throat passagewaytherethrough, said nozzle extending forwardly into said throatpassageway, an annular collar member secured to the rear end of saidring and providing a baffle surface generally normal to the longitudinalaxis of said ring and entirely rearwardly thereof, said baffle surfaceextending radially inwardly and outwardly of said ring throatpassageway, said ring being spaced from the walls of said tube to definea chamber therebetween, said radially outwardly extending portion ofsaid collar being spaced from the walls of said tube to define arestricted inlet passageway into said chamber, the forward end of saidring cooperating with the forward end of said tube to define arestricted discharge passageway from said chamber, said inlet anddischarge passageways being smaller than the cross sectional area ofsaid chamber, means for providing a volume of air to said blast tube,the air moving through said chamber constituting primary air and the airmoving through said throat constituting secondary air, and a pluralityof vanes in said chamber helically disposed relative to the longitudinalaxis of said tube for imparting a spin to the air flow therethrough,said vanes being positioned radially outwardly of said ring andforwardly of said collar member, whereby said hollow oil spray coneoperates to aspirate both primary and secondary air outwardly from saidchamber and throat in proportion to the rate of fuel flow, so that theprovision of combustion air is varied in response to changes in fuelflow rate.

6. A liquid fuel burner comprising an elongated air blast tube havingits rear end adapted to receive a flow of inlet air and having itsforward end adapted to discharge into a combustion chamber, an oil tubeterminating in a spray nozzle upstream of and closely adjacent theforward end of said tube, said nozzle when supplied with oil at apredetermined pressure serving to discharge a spray cone of oil at aflow rate within the range of 0.65 to 1.65 G. P. H., a baflie platedisposed within said tube, means cooperating with said baffle plate toposition it in spaced relation to the walls of said tube and apassageway therebetween, a generally cylindrical ring member centrallydisposed in longitudinally coaxial relation within said tube forwardlyof said bafile plate, said ring defining a central throat passagewaytherethrough, said nozzle extending forwardly into said throatpassageway, an annular collar member secured to the rear end of saidring and providing a baffle surface generally normal to the longitudinalaxis of said ring and entirely rearwardly thereof, said bafiie surfaceextending radially inwardly and outwardly of said ring throatpassageway, said ring being spaced from the walls of said tube to definea chamber therebetween, said radially outwardly extending portion ofsaid collar being spaced from the walls of said tube to define arestricted inlet passageway into said chamber,

the forward end of said ring cooperating with the forward end of saidtube to define a restricted discharge passageway from said chamber, saidinlet and discharge passageways being smaller than the cross sectionalarea of said chamber, means for providing a volume of air to said blasttube, the air moving through said chamber constituting primary air andthe air moving through said throat constituting secondary air, said ringand collar members and said baflle plate providing structural meanscooperating with the air moving through said blast tube to form a firstreduced pressure zone for said secondary air flow, and a plurality ofvanes in said chamber helically disposed relative to the longitudinalaxis of said tube for imparting a spin to the primary air flowingtherethrough, said vanes being positioned radially outwardly of saidring and forwardly of said collar member, whereby said hollow spray coneoperates to form a second reduced pressure zone and to aspirate bothprimary and secondary air outwardly from said chamber and throat inpr0portion to the rate of fuel flow, so that the provision of combustionair is varied in response to changes in fuel flow rate.

7. A liquid fuel burner comprising an elongated air blast tube havingits rear end adapted to receive a flow of inlet air and having itsforward end adapted to discharge into a combustion chamber, a bafileplate disposed within said tube, means cooperating with said baflieplate to position it in spaced relation to the walls of said tube anddefine a passageway therebetween, a generally cylindrical ring membercentrally disposed in longitudinally coaxial relation within said tubeforwardly of said baffle plate, said ring defining a central throatpassageway therethrough, an annular collar member secured to the rearend of said ring and providing a bafiie surface generally normal to thelongitudinal axis of said ring and entirely rearwardly thereof, saidbafile surface extending radially outwardly of said ring throatpassageway, said ring being spaced from the walls of said tube to definea chamber therebetween, said radially outwardly extending portion ofsaid collar being spaced from the walls of said tube to define arestricted inlet passageway into said chamber, the forward end of saidring cooperating with the forward end of said tube to define arestricted discharge passageway from said chamber, said inlet anddischarge passageways being smaller than the cross sectional area ofsaid chamber, said chamber providing a cushioning volume for regulatingan even discharge of air flow therefrom, and a plurality of vanes insaid chamber helically disposed relative to the longitudinal axis ofsaid tube for imparting a spin to the air flowing therethrough, saidvanes being positioned radially outwardly of said ring and forwardly ofsaid collar member.

References Cited in the file of this patent UNITED STATES PATENTS2,000,733 Avery Mayv7, 1935 2,136,777 Andrews Nov. 17, 1938 2,553,520Neiman May 15, 1951 2,603,280 Bernhard July 15, 1952

